Detonators



Oct. 2a, 1958 A F. I; SEAVEY Em 2,857,847

DETONATORS Filed Oct. 13, 1954 v 2 Sheets-Sheet l FIG. 2

, INVENTORS' FREDERICK RSEAVEY BY MASON E. GILL AGENT -Oct.28,1958' I F.SEAVEY E lAL 2,857,847

' DE TONATORS Filed Oct. 13, 1954 1 I 2 Sheets-Sheet 2 IN VEN TORSFREDERICK R. SEAVEY y MASON E.G|LL

AGE/VT United States Pate 2,857,847 Patented Oct. 28, 1958 DETONATORSFrederick R. Seavey, Alton, and Mason E. Gill, Dow,

llL, assignors to Olin Mathieson Chemical Corporahon, East Alton, 111.,a corporation of Virginia Application October 13, 1954, Serial No.462,054

1 Claim. (Cl. 102-865) This invention relates to detonators andparticularly to the so-called combination detonator provided with astab-type primer.

Such combination detonators are generally used to provide detonation ofthe base charge in high explosive shells and theyare normally initiatedby penetration of a firing pin into the primer. These detonators usuallycontain, in addition to the base charge, a delay or initiating chargeand a priming charge. Under optimum conditions, the time intervalbetween the penetration. of the firing pin into thepriming mix and thedetonation of the base charge is consistent, and normally this delay isvery short,

that is, it is measured in microseconds. This short delay is essentialto the proper operationof the high explosive shell in which thedetonator is carried, for it provides time for the shell to penetrateinto the body of the target before it is exploded. Under somecircumstances, however, the firing pin penetrates completely through thepriming mix and into the delay element of the detonator and in suchinstances the detonation of the base charge of the, shell is practicallyinstantaneous and the eificiency of the shell is largely lost due to itsbeing exploded exterior to the target. It has been noted that there hasbeen considerable variation in the firing time of the high explosiveshells provided with such detonators that are activated on impact; andit has now been found that such variations are in a large part due tovariations in the penetration of the firing pin into and through thepriming mix of the detonator. Thus, extra heavy impacts tend to forcethe firing pins point beyond the sensitive priming layer and into theinitiating charge normally lying below the priming mix. Such excessivepenetration causes instantaneous detonation or, at best, very shortdelays from assemblies which would produce useful delays with normalfiring pin penetration.

It is therefore an object of this invention'to provide a frictionactivated detonator having a more uniform firing time than previouslyknown detonators of thistype. It is also an object of this invention toprovide a combination detonator in which the depth of penetration of thefiring pin is controlled and in which penetration of the firing pin intothe second charge of the detonator is effectively eliminated.- Anotherobject of this invention is to provide a novel stab-initiated detonator.A further object of this invention is to provide a stab-type detonatorovercoming the disadvantages of the prior art detonators.

The manner in which these. and other objects are accomplished by thisinvention will be fully understood when the following descriptionthereof is read in connection with the drawing, in which:

Figure 1 is a sectional view illustrating an embodiment of thisinvention;

Figure 2 is a fragmentary view partially in section showing a detonatormade in accordance with this invention in firing position in aprojectile fuze; and

Figures 3, 4, 5 and 6 are perspective views of detonator components;utilized in accordance with this invention.

In accordance with this invention, generally stated,

these and other objects are accomplished by providing a detonator of thestab or impact initiated type in which a tablet or pellet of relativelyinert or friction-insensitive material is positioned between theinitiating charge and the point of entry of the firing pin into thedetonator. This is most readily achieved by providing a friction orstab-initiated detonator in which the top, or priming charge, of thedetonator is separated at least in the area of the firing pinpenetration from the second or initiating charge of the detonator by thefriction-insensitive or inert tablet or pellet. The tablet or pellet offriction-insensitive material is so positioned between the primingcharge and initiating charge so as to absorb any excess penetration ofthe firing pin and prevent it from entering into the initiating charge.Thus, the priming and initiating charges are separated from one anotherat least in the central portion of the detonator by the pellet ofconsolidated friction-insensitive material. Such a tablet can extend tothe periphery of the charges, but is preferably centrally located andhas a diameter between about 40% and about of the diameter of thedetonator. The thickness of the'tablet can vary within wide limits andit is only necessary that the tablet be sutficiently thick to absorb anyexcess penetration of the firing pin, while not preventing thetransmission of the fiame or explosive wave between the charges.

Tablets ,7 of widely divergent configurations can be utilized inaccordance with this invention. Suitable shapes include conical,cylindrical, rectangular and the like.

The composition of the tablet which is used in accordance with thisinvention to prevent by-passing the explosive stimulus through thepriming mix may vary appreciably. It is only essential that it be madeup of frictioninsensitive or inert materials. The tablet or pellet can,

for example, be composed of nylon, wood pulp, talc,

chalk, polyethylene, rubber, neoprene, starch or rosin, and mixturesthereof, as well as other minerals and natural and synthetic resins.Explosive materials incapable of initiation by the action of the firingpin can also be employed in the pellet. Suitable explosive compoundsinclude, for example, trinitrotoluene, cyclonite, tetryl,pentaerythritol tetranitrate, and ammonium nitrate. This tablet can beprepared by ordinary consolidating methods and is preferably prepared inconventional pelleting equip ment. Alternatively, the tablets can beprepared by subdividing extruded plastic or resinous resilient bodiesinto appropriate shapes.

The terms friction-insensitive and inert as used in this specificationand in the appended claims are synonomous and denote compounds orcompositions incapable of violent decomposition or chemical reactioncaused by normal penetration by the firing pin.

This tablet can be imbedded in the priming mix, in the uppermost portionof the initiating charge, or a portion of the tablet maybe located inone charge while the remainder of the tablet extends into the othercharge. In

those cases where it has been found desirable to separate the primingand initiating charges with afoil of paper or metal such as aluminum,the tablet of this invention is more securely positioned in thedetonator by cementing it to the foil. In such instances, the tablet isof course contained entirely within the priming charge or the initiatingcharge and the foil serves the two-fold purpose of separating theadjacent explosive charges and of positively positioning the tablet.

The explosive train of the detonatorforms'no part of the presentinvention and any suitable explosive ingredia ents can be used withequal efliciency, provided only that the inert pellet is positionedabove the initiating charge so as to serve as a cushion for anysevereirnpact by the,

' firing pin. Thus, the primer charge can be any of thestandardpercussion priming mixes, for example, lead styphnate,tetra'cen'e, and/ or mercury fulminate, together with suitable fuels,oxidizers and abrasives, or mixtures of potassium chlorate, antimonysulfide and lead sulfocyanate; and the like; while the"init'iatingcharge can, for example, be lead az'ide, diazodinitrophenol with orwithoutpotassiumchlorate,or'mercury fulminate, and mix tu'res thereof.Any suitable base'charge such as trinitrotoluene, cyclonite, PETN,hexanitromannite, tetr'yl, and the like can be' utilized.

In'order thatthe inventionmay be further clarified and more fullyunderstood, the following is a detail description of a preferredembodiment thereof.

As shown in 'Figu'rel of thedrawing, the detonator is provided-with ametal'case '1, preferably aluminum, which is loaded'witha base charge2'0f cyclonite and initiating charge 3 of lead azide and apriming charge4 consisting of normal and basic lead styphnate, aluminum, antimonysulfide, andb arium nitrate; These charges are consolidated and loadedat pressures between about 10,000 and 20,000 pounds per square inch andare retained in place by means of aluminum discs 5 and 6 at either endof the case. The tablet 7 in this example is composed of consolidatedtalc and is imbedded in the initiator charge so as to protect it fromany possible excess penetration of the firing pin. This modifiedtruncated conical pellet is centrally located and has a diameter greaterthan onehalf of the diameter of the detonator itself. In accordance withthe preferred embodiment of this invention, the pellet is seated in adepression 8 in the priming mix, and extends through a major portion ofthe initiator charge. The thickness of the tablet is not at all criticaland it will be readily appreciated that it is only necessary for thetablet to be sufliciently thick so as to extend beyond the maximumpossible point of penetration of the firing pm.

The detonator as described in the above embodiment -was prepared byinverting the detonator case 1 and closing one end thereof with the thinaluminum disc 5, the priming charge 4 was then weighed and pressed intoposition at a pressure of about 20,000 pounds per square inch. In thepreferred embodiment shown,'it will be noted that the priming charge 4was stepped at 8 so as to provide a cylindrical recess to accommodatethe pellet 7 of inert material. This recess is not essential to theinvention but it does provide one convenient means of positivelypositioning the pellel and preventing its migration during thesubsequent loading operations. After the priming mix had been pressedinto place, the pellet 7 was positioned as shown with its base restingin the recessed portion of the priming mix. With the pellet in place,the initiating charge 3 was loaded into the detonator case about andaround the pellet and was then pressed at about 20,000 pounds per squareinch. In like manner, the base charge 2 was then placed in the case andwas also consolidated at the same pressure. The case was then closed byplacing the aluminum base plate 6 in position and then crimping the endof the detonator case over it.

Figure 2 of the drawing shows a detonator prepared in accordance withthis invention in firing position in a typical projectile fuze. As shownin this figure, the firing pin 9 has penetrated completely through thepriming mix 4 and into the inert pellet 7. Under normal conditions thepenetration of the firing pin would not be so great, but under severeimpact or in instances where the tolerances are accumulative it has beenfound that with the" ordinary stab-initiated detonator the firing pinoften penetrates into the initiating mix and thus a negligible delay orinstantaneous detonation will result. As particularly well illustratedin this figure, however, such excess penetration is effectivelyeliminated by the inclusion of the inert pellet 7 into the detonator.Since, as is the case in practically all impact initiated projectiles,the extent of the penetration of the firing pin is limited by theshoulder 10 of the pin coming in contact with the housing pin willprevent premature activation of the"initiating charge resulting frominadvertent penetration of the firing pm.

Figures 3, 4, 5 and 6 serve to illustrate some of the modifications thatcan be made in the shape of the inert pellet used to obtain the benefitsof this invention. As shown in Figure 3, the pellet can be in the formof a truncated cone whose lower portion has been modified so as to forma cylinder. Such a modification is not critical and an unmodifiedtruncated cone can be used provided that measures are taken to preventbreakage of the edges around its base. In some instances it may bepreferable to use a cylindrical pellet as shown in Figure 4.

When it is essential or desirable to prevent intermixing of theinitiating and priming charges, such intermixing can be eliminated bymeans of a foil betwen the charges and in such instances the inertpellet is advantageously cemented to the foil prior to its insertioninto thedeten'ator. Thus, the foil serves not only as a separating meansbut also as a positioning element for the pellet.' Such an assembly isillustrated in Figure 5 in'which the pellet has been cemented to a thinaluminum foil 12.

It will be noted that the pellet'of Figure 6 does not have a cylindricalbase but'rather it'is provided with asubstantially square base havingrounded edges. When this type of a pellet is used, it is preferred'thatthe rounded edges 13 contact the inside wall of the detonator case whilethe flame or explosive wave from the priming mixture is transmitted'tothe initiating charge through the spaces occurring between the straightportions 14 in'the base of the-pellet and the shell wall; In this way,the inert tablet is maintained in an operative position while a path forthe transmission of the explosive wave through the detonator ispreserved.

The detonator as illustrated hereinbefore provided substantially uniformfiring times regardless of the degree of penetration by the firing pininto or through the priming mixture. When the firing pin penetratescom"- pletely through the priming'mix, the premature initiation" of theinitiating charge 3 is prevented by the cushioning pellet 7 and in allinstances the explosive stimulusmust' necessarily be transmitted fromthe priming charge to the initating charge.

While the above embodiment depicts a detonator pro vided with a metalcase and a particular explosive train,

it is not to be inferred that this invention is limited to such details.On the contrary, detonators having plastic or metal cases containing agreat variety of explosives can be utilized to achieve the desirableresults of this invention; and it is to be understood that the featuresof this invention can be advantageously applied to all types ofdetonators that are initiated by impact or'stab action.

From the foregoing, it is evident that thisinventi'on accomplishes itsobjects in providing a novel stab-initi ated detonator inwhichvariations in the delay period charge, a cushion pellet of inertmaterial and an' initi'-' ating charge adapted to be activated by thepriming charge, the priming charge being positioned 'abovethe initiator,the pelletbeing positioned below the=priming charge and above thatportion of the initiator located' in an extrapolation of the normalpathof'the' firing piithe References Cited in the file of this patentUNITED STATES PATENTS Cartwright Feb. 24, 1920 Anderson July 21, 1931Petter Oct. 27, 1936 King Dec. 7, 1937 Hibbs Sept. 28, 1943 Amthor Mar.19, 1946 Morris May 11, 1948

